1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method, and a program, which are adapted to perform a kickback processing with respect to an image to be processed (hereinafter referred to as a processed image) where a figure having a high lightness is placed in a background image using rich black or the like.
2. Description of the Background Art
Conventionally, an image for a color printing is composed of a plurality of color components (for example, the color components of C (cyan), M (magenta), Y (yellow), and K (black)), and can be printed on a printing paper through printing plates made for the color components, respectively. When black is expressed in the image for the color printing, not only K-color but also other color components may be added to express a deeper black (so-called “rich black”).
In cases where in this image for the color printing, a blank character is placed in a background image using rich black, the color components other than K-color (e.g., C, M, and Y) may jut out into the blank character by a slight misregistration of the printing positions of the respective printing plates on the printing paper. In order to prevent this disadvantage, in the process of an image processing before making plates, there is performed the processing for removing color components other than K-color in a region of a predetermined width around the blank character (hereinafter referred to as a “kickback processing”). The kickback processing can be handled as a kind of trapping being an image processing for preventing image deterioration due to plate misregistration.
In the conventional kickback processing, however, the color components other than K-color are removed uniformly in the region around the blank character when the background image is an uneven image (namely when the density value of the K-color in the background image is not constant). Therefore, the blank character in the region having a low density value of K-color will seem bold, and in some cases, this is unfavorable in terms of the appearance of the image. For example, when performing a kickback processing to a processed image 30, as shown in FIG. 6, if the M-color around a character 32 is removed, the upper half of the character 32 will seem bold in the processed image 30, as shown in FIG. 13.
This is a problem generally arises when the kickback processing is performed to a processed image where a figure having a high lightness is placed in a background image composed of a main color component having a relatively low lightness and a sub color component having a relatively high lightness, rather than a problem peculiar to the case where the blank character is placed in the background image using rich black.